Home Stand-By Generator

[EEC]

What are the wiring changes needed to existing loadcenters when installing Automatic Transfer Sw to line side of loadcenters and load side of ATS as far as grounding or bonding?
Also at the generator, what type of grounding/bonding does the code require at that location?

 

[LarryFine]

What are the wiring changes needed to existing loadcenters when installing Automatic Transfer Sw to line side of loadcenters and load side of ATS as far as grounding or bonding?

The panel must be rewired as if it were a sub-panel, meaning isolating the entire neutral system from the enclosure and EGC's. This unfortunately means that 3-wire large-appliance circuits that use the neutral as the EGC must be converted to 4-wire.

Also at the generator, what type of grounding/bonding does the code require at that location?

This depends on whether the neutral is bonded within the generator: if it is, you must switch the neutral, but if you don't switch the neutral, the bond must not be made within the generator.


Most residential ATS's do not switch the neutral, and in addition to the above, the grounding electrodes must be rewired to be made within the service disconnect, whether within, or ahead of, the ATS.

 

[A/A Fuel GTX]

Larry....Are there definitive drawings somewhere that show the different scenarios utilizing generator power, ie, transfer switch, no transfer switch, etc. This seems to be an area of confusion for a lot of us. A Mike Holt type drawing would be great.

 

[tom baker]

Tom I agree its really confusing! Mike Holt has some good drawings that show what happens if the system bonding jumper is installed when its not supposed to be. Perhaps I can post one later.

 

[Bea]

1- ATS will need to be service rated
2- All bonding will need to acure at ATS
3- floating neutral from grounds at existing opanel as now subpanel 4 wire
5-does the ATS switch the neutral conductor if not provide for 4 wire to generator neutral floats at generator. If the neutral is switched by ATS then 3 wire to generator must install grounding electode system and bond neutral down at generator.

 

[A/A Fuel GTX]

Tom I agree its really confusing! Mike Holt has some good drawings that show what happens if the system bonding jumper is installed when its not supposed to be. Perhaps I can post one later.

That would be great if you could do that, Tom.